"Deadweight" is used to describe any object or person that weighs something else down. For example, the weight of passengers and cargo loaded into a vehicle is referred to as deadweight -- meaning it is weight in addition to the vehicle itself that the engine must haul. In social situations, deadweight refers to an individual who metaphorically weighs down a larger group of people. This could be someone who doesn't contribute a fair share toward a collaborative work project, or a gloomy individual who emotionally weighs-down others.
In economics, the term "deadweight loss" refers to two situations in which there is a loss of economic efficiency. One example of deadweight loss is when a producer raises the price of an item; such that the price excludes potential buyers. The reverse situation is also considered a deadweight loss. When a producer lowers the cost of an item below the optimized cost; such as due to a government subsidy for the item's production, some consumers will purchase the item even though their marginal benefit from the item is less than its real cost. In both situations, resources are not utilized optimally to gain the benefit of the full economic interaction. This loss of efficiency is referred to as deadweight loss.
Indicated by the abbreviation DWT, deadweight tonnage refers to the load of a cargo ship. It refers to either the total amount of weight onboard a ship, or the amount of weight a ship can safely carry. The weight of the ship is not included in the measurement of deadweight tonnage. Rather, it refers to the total weight of cargo, passengers and water used for ballasts.
The term deadweight is derived from the combination of the words "dead" and "weight." Rather than "non-living," the word "dead" is used to describe inertness. "Weight" can either refer to a literal weight or a metaphoric weighting effect, such as in the case of a person or event that is emotionally deterrent. The first known use of the term was in 1659.